Updated contributors guide

CONTRIBUTING.md

@@ -2,21 +2,30 @@
 
 ## Preparation
 
-You'll need to have Python 3.6 available for testing.
+You'll need to have Python 3.7 or newer available for testing.
 I recommend using [pyenv][] for this:
 
-    $ pyenv install 3.6.5
-    $ pyenv shell 3.6.5
+    $ pyenv install 3.7.13
+    $ pyenv local 3.7.13
 
+Ideally, you should also have newer versions as well:
 
-## Setup
+    $ pyenv local 3.10.4 3.9.9 3.8.12 3.7.13
 
-Create a fresh development enviroment, and install the
-appropriate tools and dependencies:
+
+## Testing
+
+Create a fresh development environment, and bootstrap thx: 
 
     $ cd <path/to/thx>
-    $ make venv
-    $ source .venv/bin/activate
+    $ python -m venv venv
+    $ source venv/bin/activate
+    (venv) $ pip install -U pip -r requirements-dev.txt
+    (venv) $ pip install -e .
+
+Run the test suite from your bootstrapped version of thx:
+
+    (venv) $ thx
 
 
 ## Submitting
@@ -27,7 +36,6 @@ that you have done the following:
 * Documented changes or features in README.md
 * Added appropriate license headers to new files
 * Written or modified tests for new functionality
-* Used `make format` to format code appropriately
-* Validated and tested code with `make lint test`
+* Run `thx` to run the formatter, and passed the test suite and all linters.
 
 [pyenv]: https://github.com/pyenv/pyenv